Conventionally, a power conversion system has been proposed in which a snubber circuit is connected between output terminals of a power supply circuit that supplies direct-current power to a power conversion circuit including a switching element, and a surge voltage generated in the power conversion circuit is absorbed by the snubber circuit, for example, as described in Patent Document 1 (identified below). In this power conversion system, a capacitor circuit in which two capacitors are connected in series is used as the snubber circuit. This makes it possible to prevent short circuit between the output terminals of the power supply circuit even if a short-circuit fault occurs in one of the capacitors connected in series, thereby preventing flow of a high current in the power conversion circuit. It is noted that, in this kind of power conversion system, a snubber circuit is sometimes connected, for example, in parallel with a capacitor for smoothing. A module integrating the capacitor for smoothing and the snubber circuit is sometimes referred to as a capacitor module.
Patent Document 1: Japanese Patent Application Laid-Open No. 2013-252009.
However, according to the configuration described in Patent Document 1, the electrostatic capacitance of the whole capacitor circuit changes upon occurrence of a short-circuit fault in one of the two capacitors in a case where, for example, low-dielectric-constant ceramic capacitors or film capacitors are used as the capacitors that constitute the capacitor circuit. This undesirably changes surge voltage absorption characteristics of the capacitor circuit.